Arrangment for adjusting moisture content of the soil of a sports field

ABSTRACT

Arrangement for adjusting the soil moisture of a sports field, the structure (S) of which contains a field surface (P), a tread layer ( 9 ) below the field surface (P), and a support layer (T) formed below the tread layer ( 9 ), and the tread layer ( 9 ) is separated from the support layer (T) by a separating layer (V), a network of drainage pipes ( 6 ) is arranged in the support layer (T) and connected to a pool (M), and the support layer (T) is lying on a waterproof film ( 4 ). The basin (M) is provided with a filling valve ( 26 ) and a sluice opening ( 13 ) the lower flow level (A) of the latter is arranged below the upper level of lower crushed stone layer (A).

The invention relates to an arrangement for adjusting the soil moisture content of a sports field, e.g. a racecourse, a ball game field, the field structure of which contains a field surface, a tread layer below the field surface, and a support layer formed below the tread layer, and the tread layer is separated from the support layer by a separating layer, a network of drainage pipes is arranged in the support layer and connected to a pool, and the support layer is lying on a waterproof film.

Sports fields with various sandy, soil and/or natural/synthetic turf soils, especially horse racing, ball or obstacle courses, are difficult to keep wet, especially in hot, windy weather, while water can accumulate on their surface for even longer in rainy weather. Proper use of the tracks, performing trainings and competitions becomes difficult or even impossible in both cases, because the degree of usability of the track is determined by the condition of the field surface for the given sport, which essentially means the right amount of soil moisture, in the case of a professionally installed track.

Wetting is most easily solved by surface watering, which is usually done from the edge of the track, with water cannons or water wagons installed along the sides of the track.

However, this is a water-wasting process consuming both time and energy, having a significant demand in terms of personnel and machinery, and therefore it is costly. In addition, it does not ensure even wetting of the surface of the field, because the amount of water applied and the uniformity of the application depends on the attention of the sprinkler, but also on the order in which certain parts of the track are watered. The water applied in this way evaporates quickly in warm, windy weather, so the quality of the field surface can change significantly during longer training or competition, that is this solution does not provide equal conditions for competitors; the surface watering required during the race takes valuable time from racing.

One of the prior art solutions designed to overcome these disadvantages is a tidal system used to drain and moisten the field. The essence of this is that the rainwater drainage system, ie the dewatering system, can simultaneously moisten the tread surface.

With this solution the soil of the sports field will be built into a waterproof ditch. At the bottom of this there is a drainage system connected to a water outlet and inlet device located outside the track. The tread surface is built on the leaking system, but these two layers, i.e. the substructure layer next to and above the leaking pipes, consist of the same fine-grained material, eg. sand. To separate the two layers, a plurality of different types of perforated cassettes is incorporated in order to achieve stabilization of the upper tread surface. The cassettes must be laid down one by one and fastened together so that they do not move, as a possible movement is a serious source of danger e.g. for both the rider and the horse. At the same time, both the fine-grained bottom loading and the cassette separator layer inhibit and delay the rapid drainage of rainwater, which can have the consequences of forming puddles on the field, or riding track. To moisten the field, water is injected through an external drainage point through this leaking system. This feed water must reach the tread surface from the leaking pipes through the conventional fine-grained bottom filling and the openings in the separator layer cassettes, which results in slow and uneven wetting due to the high hydraulic resistance of the fine-grained and cassette-covered substructure. This can mean that during the warmer hours of the day, wetting is inadequate, uneven, and becomes dusty on some surfaces of the track, while puddles can form elsewhere. A further disadvantage is that if the upper tread layer has to be replaced, the entire cassette separating layer has to be picked up, because the recesses of the cassettes are filled with the material of the upper layer to be removed.

WO 2015124260 A8 discloses a riding field with a humidification and drainage system, for which humidification and drainage pipes connected to a water source are arranged in the waterproofed pool of the system. Tubes are arranged under an elastic mat comprising at least one base layer made of water-permeable, preferably closed-cell and cross-linked PE or PET plastic cassettes. A layer of water-permeable, preferably non-woven PET geotextile bonded to the base layer is arranged on the upward-facing side of the flexible mat. Each tube is covered on at least the upward-facing side by a water-permeable filter cloth, which is preferably formed with an actual opening size of between 0.08 mm and 0.1 mm. The pipes are embedded in a sandy crushed stone bed and connected to a water well, with fine quartz sand above the elastic mat.

In this system, therefore, both wetting and the drainage of excess water are solved by elements located in the ground of the field, thus eliminating conventional watering. The disadvantage of the system is that both sand-crushed fine-grained quartz sand filling and the thick separating layer of plastic cassettes hinder the rapid drainage of rainwater, which can temporarily forms puddles on the field. Water pressed to wet the track must pass from the leaking pipes through the fine-grained filling around them, then through the openings of the plastic cassette separator layer and the geotextile covering it, through the tread sand to the tread surface, which is a very slow and unequal wetting process, since the understructure covered by the cassettes has a high hydraulic resistance and, on the other hand, the water can come into contact with the tread sand by the same area as the area of the geotextile covering the cassette system is, so on the smallest possible surface. This can mean that wetting is inadequate, uneven, slow and becomes dusty on some surfaces of the field during the warmer hours of the day, while elsewhere over-wetting can occur and sand spread on the geotextile can slip. A further disadvantage is that the installation of the known system is extremely expensive, mainly due to the cost of manufacturing and disposing of the cassette system forming the separating layer.

Our object, therefore, is to overcome the disadvantages of prior art solutions and to develop a sports field drainage and humidification system that is inexpensive, easy to install and operate, while both draining and wetting as quickly and smoothly as possible. The removal of a worn top layer should be possible without removing and reinstalling the separating layer.

We have realized that if a reservoir volume filled with crushed stone instead of sand is formed below the field surface, and a simple geogrid with excellent water permeability is laid on the crushed stone layer, instead of a cassette system with high hydrostatic resistance, by placing a geotextile under the geogrid and adjusting the water level of the reservoir volume continuously and automatically, then the field surface can be optimally wetted in dry weather, while the excess water can be drained through the drainage pipe network operating in the crushed stone bed laid down on a waterproof foil in rainy weather, without a risk of making too dry or too wet surface, thus continuously ensuring an optimal, wetted sandy tread surface on which there are no puddles even in the event of heavy rain, and the chances of sand slipping are also reduced.

We have achieved our object by providing an arrangement for adjusting the soil moisture of a sports field, the structure of which contains a field surface, a tread layer below the field surface, and a support layer formed below the tread layer, and the tread layer is separated from the support layer by a separating layer, and a network of drainage pipes is arranged in the support layer and connected to a pool, and the support layer is lying on a waterproof film, wherein the separating layer is formed of a geogrid, and the support layer contains an upper crushed stone layer and a coarser, lower crushed stone layer connected to it from below, and between the upper crushed stone layer and the geogrid a geotextile is arranged, and the film are folded over the edges of the field surface above the same, and between the geotextile and the foil a geogrid strip coated with a geotextile material is arranged, and the geotextile material is in contact with the geotextile plate, and the basin is provided with a filling valve and a sluice opening the lower flow level of the latter is arranged below the upper level of lower crushed stone layer.

A drain pipe is connected to a collecting pipe connecting the basin and the drain pipe.

The lowest level of the collecting pipe is arranged below the lower flow level.

The upper crushed stone layer is made of crushed stone with a grain size of 4 to 11 mm. 5.

The lower crushed stone layer is made of crushed stone with a grain size of 11 to 22 mm.

The basin is divided into a smaller first chamber and a larger second chamber, and the chambers are connected by means of the sluice opening, and the collecting pipe is connected to the first chamber.

The second chamber is provided with an overflow opening with a lower flow level arranged at a level lower than the lower flow level of the sluice opening.

The filling valve is arranged to open into the second chamber, and the two chambers are connected by means of a pipe connected to the submersible pump located in the second chamber, and a water level sensor is arranged in the first chamber.

The pool is equipped with an automatic control means to which a remote-controlled sluice for operating the sluice opening, the submersible pump, the water level sensor and the remote-controlled filling valve are connected.

The field surface is the surface of the tread layer.

The field surface is a lawn mat comprising lawn species planted in a layer of soil arranged on the tread layer.

The field surface is a synthetic grass layer arranged on the tread layer.

The invention will now be described in more details with reference to the accompanying drawings. In the drawings

FIG. 1 shows the layers arranged below the field surface of the arrangement according to the invention with basement pipes,

FIG. 1a . shows an enlarged view of a geotextile strip arranged at the edge of the field surface,

FIG. 2 shows a detail of a separating grid,

FIG. 3 shows the arrangement of drainage pipes and collecting pipes in the field structure in top view,

FIGS. 4a and 4b . shows a cross-section of the installation of drainage pipes and collecting pipes, and

FIG. 5. a cross section of a two-chamber control basin.

FIG. 1 shows a vertical section of the layered field structure S with basement pipes arranged below the field surface P of the sports field arrangement according to the invention. In a preferred embodiment suitable e.g. for performing horse racing as shown, there is a tread layer 9 below the field surface, made of quartz sand and textile chips, which forms the field surface P itself, and which has a thickness preferably between 10 and 15 cm, and is wetted in a capillary way up to the field surface P. In another preferred embodiment, which is not shown in the figure, and is suitable e.g. for performing ball games, the field surface P is a turf arranged on the tread layer 9, the material of which is made e.g. of lawns planted in a layer of soil known from the art, and which is capable of discharging its moisture content into the tread layer 9 and, if appropriate, for absorbing moisture therefrom. In a further preferred embodiment, the field surface P can even be a turf mat made of synthetic fibers arranged on the tread layer 9, which is also well known in the art and is capable of absorbing and releasing moisture. Below the tread layer 9, a grid 8 is placed as a separating layer V, which e.g. a simple grid made of high-density polyethylene (HDPE), the details of which are shown in FIG. 2. The preferably about 1 cm thick grid 8 has a high liquid permeability, which allows a large amount of water to pass quickly through the grid 8 even when its pressure is low. Determining the size of the grid holes 81 of the grid 8 shown in FIG. 2 by a series of experiments, it was found that the grid hole 81 is preferably rectangular, with a hole size of preferably 10-16×10-16 mm, most preferably 12×12 mm.

Referring to FIG. 1, a geotextile plate 8 a made of polypropylene (PP) preferably plastic to the grid 8 is located below the grid 8, but it can be made of other, plastic weldable, fabric-like, non putrefiable material. The geotextile plate 8 a also permeates the liquid, but not the sand grains of the tread layer 9 located in the holes of the grid 8. The upper tread layer 9 rests stably and friction tightly on a separating element consisting of 8 grid and 8 a geotextile having a liquid permeability of about 221/s·m², ensuring the stability of the field surface P.

In order to increase resilience of the field surface P, in a preferred embodiment, a 25-30 mm thick layer of crushed rubber grit (not shown) may be placed under the geotextile plate 8 a to spare the feet of athletes/horses and thus protecting their health. Laying the separating element consisting of the grid 8 and the geotextile 8 a is quick and easy. Thus, the bonding task of a conventional cassette separator does not occur.

An upper crushed stone layer 2 b as a support layer T is arranged under the geotextile plate 8 a. The stones forming the layer 2 b preferably have a grain size of 4-11 mm. The layer 2 b is spread on a further, coarser lower crushed stone layer 2 a, the grain size of which in the embodiment shown is between 10 and 22 mm. Forming the grid 8 and the geotextile plate 8 a according to the invention, an even and flexible load distribution acting on the crushed stone layer 2 a, 2 b can be achieved, while effectively preventing the horizontal slippage of the quartz sand forming the layer 9 during training, competitions and track maintenance.

Below the stone layer 2 a, a foil 4 of high density polyethylene (HDPE) fibers is arranged on a 20-30 mm thick complanating sand layer H spread on a suitably compacted subsoil 1. The tensile strength and flexibility of the foil 4 provide flexible support for the layers forming the field structure, and its watertight surface is resistant to damages occurring during the mechanical spreading and compaction of the crushed stone layers 2 a, 2 b. The foil 4 and the grid 8 and the geotextile plate 8 a are folded on the edges Pp of the field surface P as shown in FIG. 1 in order to prevent water from lateral leaking out of the track structure S. The folded foil 4, the grid 8 and the geotextile plate 8 a it can rest e.g. on a side wall 18 formed along the edge Pp of the field surface P. The material of the side wall 18 is preferably monolithic concrete, to which a railing 19 and a curb 21 can be connected. Due to the fact that the vertical movement of water in the pool-like field structure S is very fast, it is necessary to allow the air in the field structure S to escape when the water level is raised, otherwise the buckling of the tread layer 9 must be expected. To prevent this, as shown enlarged in FIG. 1a , a geotextile strip 22 coated with a geotextile material is arranged between the grid 8 folded on the side wall 18 and the folded foil 4 so that the geotextile material is in contact with the geotextile plate 8 a. This creates a thin gap between the curb 21 and the layer 9, which runs along the entire edge Pp of the field surface P and through which the air can flow freely between the environment and the track structure S.

The described field structure S forms a volume watertightly isolated from the surrounding soil, from which the drainage pipes 6, preferably 80-120 mm in diameter, laid on the foil 4, and the connected larger 160-315 mm in diameter collecting pipes 7 connected to them and laid within the layer of sand H and passing through a cover collar G, lead to a basin M arranged outside the field structure S, as shown in FIG. 3 in a top view.

As can be seen in FIGS. 4a and 4b , only the collecting pipes 7 (FIG. 4b ) are embedded in the ground 1, so that the thickness of the part of the field structure S above the collecting pipes 7 is preferably only 25-30 cm (FIG. 4a ), in contrast with a layer thickness of 70-80 cm of prior art solutions, which allows to save on both the material and the work involved in installation.

Drain pipes 6 are connected to the 7 collecting pipes directly, through a hole drilled with a core drill, without any intermediate fitting, and preferably approx. at a 45-degree angle. By this solution one can save about hundred “T” profiles in the case of a sports field according to the illustrated embodiment. A protective-stabilizing geotextile layer 5 similar to the geotextile 8 a is spread on the collecting pipes 7 embedded by 25-30 cm in the sand layer H laid on the foil 4 and on the ground 1. In the crushed stone layers 2 a, 2 b, the water moves rapidly against a small resistance, which, in addition to storing the water, solves problems of both the immediate drainage of the rainwater and the rapid introduction of the water required for wetting. The collecting pipes 7 preferably open into a two-chamber basin M provided with control means 15 and installed longitudinally next the field structure S, as shown in FIG. 5, below the water level of the field structure S, preferably below the level of foil 4, so that they get across the foil 1 in a watertight collar G.

The collecting pipes 7 are in direct communication with the first chamber 11 of the two-chamber pool M, which is connected to the second, larger volume chamber 12 of the two-chamber pool M by a remote-controlled sluice opening 13. The lower flow level A of the sluice opening 13 is below the lower crushed stone layer 2 a, in this embodiment below the same level of the film 4, so that the field structure S can be safely emptied to the level of the film 4 if necessary. The water level of the chamber 11 is always the same as the water level stored in the field structure S due to a design corresponding to a communicating vessel. In the event of precipitation, the water level in the field structure S and consequently in the chamber 11 also rises. The water level sensor 16 of the chamber 11, e.g. a pressure measuring cell located in a protective tube 10, sends a signal corresponding to the change in water level to the control means 15, which opens the lockable sluice opening 13. Thus, the excess water entering the layer 9 is discharged from the field structure S into the chamber 12 substantially immediately before it can flood the field surface P. The overflow of the second larger chamber 12 for storing operating water is prevented by the lower overflow opening 23 having a lower flow level situated below the lower flow level A of the sluice opening 13, through which the amount of water that can no longer be stored enters the open air or an additional storage unit. If there is a minimum water level in the chamber 12, which is monitored by a level sensor 17, the control means 15 rises it again by opening a valve 26 connected to a water source. The water level in the chamber 12 is set to a minimum in order to have the largest possible storage capacity to receive the rainwater, which can be economically recycled for wetting the field surface P, e.g. instead of using expensive, cleaned mains drinking water.

If it is required to wet the field surface P and the water level of the chamber 11 is below the level of the geotextile 8 a, a submersible pump 14 raises the stored operating water back into the chamber 11 through a pipe 14 a, thus raising the water level in the field structure S until the water level reaches the level from which sufficient moisture flows up in the layer 9 near the field surface P due to the capillary effect.

This quick and direct control prevents the surface P from being flooded by a possible downpour and even puddles cannot be created, thus ensuring weather/precipitation-independent use, which is essential, especially during races. The control means 15 can be controlled via the Internet, even with a smartphone. The control means 15 is preferably provided with a recording and monitoring system which monitors and records data on water consumption, energy consumption, temperature change, as well as the time and result of the interventions, charging and discharging time intervals and the occurrence of rainfalls. Data series can be displayed e.g. in graphical form on a remote screen. The two-chamber pool M can be covered with a lightweight roof structure that protects the M pool equipment as well as the control means 15 from the effects of the weather.

In a preferred embodiment of the arrangement for controlling the soil moisture of a sports field according to the invention, the layer order of the field structure S is as follows:

-   -   a tread layer 9—120 mm in thick, washed quartz sand or         sand-textile mixture,     -   grid 8—10 mm thick, GM720 geogrid, extruded flexible mesh,     -   geotextile plate 8 a—of 200 g/m²,     -   layer 2 b—50 mm thick crushed stone with a grain size of 4-11         mm,     -   layer 2 a—100 mm thick crushed stone with a grain size of 11-22         mm,         -   geotextile 150 g/m2,     -   foil 4—BTL 30A pond foil,     -   sand layer H—20-30 mm sand cover,         -   compacted subsoil 1.

The advantage of the arrangement for adjusting the soil moisture of a sports field according to the invention over the prior art solutions is that the thickness of the field structure S can be reduced by at least half, thus allowing a cheaper and faster construction than before, and the grid 8 and geotextile plate 8 a are significantly cheaper and provide a more even and resilient load distribution on the crushed stone layer 2 b, but at the same time greatly inhibit the horizontal displacement of the tread layer 9 during training, competitions, track maintenance, and folding up of edges of the foil 4 above the upper plane of the layer 9 guarantees that no water can drain out of the system uncontrollably, and that a geogrid strip 22 provided with a geotextile installed in an inverted position between the grid 8 and the folded part of the foil 4 allows the necessary movement of air. Another advantage is that it saves water because it uses rainwater originated from the field structure S for rewetting it, thus significantly reducing the use of irrigation water from the water network or wells as compared to conventional fields, while the water level of the field structure S can be controlled easily, quickly and reliably. 

1. An arrangement for adjusting the soil moisture of a sports field, the structure (S) of which contains a field surface (P), a tread layer (9) below the field surface (P), and a support layer (T) formed below the tread layer (9), and the tread layer (9) is separated from the support layer (T) by a separating layer (V), a network of drainage pipes (6) is arranged in the support layer (T) and connected to a pool (M), and the support layer (T) is lying on a waterproof film (4), wherein the separating layer (V) is formed of a geogrid (8), and the support layer (T) contains an upper crushed stone layer (2 b) and a coarser, lower crushed stone layer (2 a) connected to it from below, and between the upper crushed stone layer (2 b) and the geogrid (8) a geotextile (8 a) is arranged, and the film (4) are folded over the edges of the field surface (P) above the field surface (P), and between the geotextile (8 a) and the foil (4) a geogrid strip (22) coated with a geotextile material is arranged, and the geotextile material is in contact with the geotextile (8 a) plate, and the basin (M) is provided with a filling valve (26) and a sluice opening (13) the lower flow level (A) of the latter is arranged below the upper level of lower crushed stone layer (A).
 2. The arrangement according to claim 1, wherein a drain pipe (6) is connected to a collecting pipe (7) connecting the basin (M) and the drain pipe (6).
 3. The arrangement according to claim 2, wherein the lowest level of the collecting pipe (7) is arranged below the lower flow level (A).
 4. The arrangement according to claim 3, wherein the upper crushed stone layer (2 b) is made of crushed stone with a grain size of 4 to 11 mm.
 5. The arrangement according to claim 4, wherein the lower crushed stone layer (2 a) is made of crushed stone with a grain size of 11 to 22 mm.
 6. The arrangement according to claim 5, wherein the basin (M) is divided into a smaller first chamber (11) and a larger second chamber (12), and the chambers (11, 12) are connected by means of the sluice opening (13), and the collecting pipe (7) is connected to the first chamber (11).
 7. The arrangement according to claim 6, wherein the second chamber (12) is provided with an overflow opening (23) with a lower flow level (B) arranged at a level lower than the lower flow level (A) of the sluice opening (13).
 8. The arrangement according to claim 7, wherein the filling valve (26) is arranged to open into the second chamber (12), and the two chambers (11, 12) are connected by means of a pipe (14 a) connected to the submersible pump (14) located in the second chamber (12), and a water level sensor (16) is arranged in the first chamber (11).
 9. The arrangement according to claim 8, wherein the pool (M) is equipped with an automatic control means (15) to which a remote-controlled sluice (Z) for operating the sluice opening (13), the submersible pump (14), the water level sensor (16) and the remote-controlled filling valve (26) are connected.
 10. The arrangement according to claim 1, wherein the field surface (P) is the surface of the tread layer (9).
 11. The arrangement according to claim 1, wherein the field surface (P) is a lawn mat comprising lawn species planted in a layer of soil arranged on the tread layer (9).
 12. The arrangement according to claim 1, wherein the field surface (P) is a synthetic grass layer arranged on the tread layer (9). 